1. Field of the Invention
The present invention relates to a photoelectric detector that includes a member for emitting a light signal and a member for receiving a reflected light signal. The photoelectric detector outputs information indicative of the presence of a target to be detected or a distance to the target to be detected along a path of the light signal.
2. Discussion of the Background
Photoelectric detection devices are well known and can usually be divided into two categories. The first category includes systems that are called thru-beam type systems. The emit member and the receive member of these devices are placed at two points distanced apart and the target is detected when the target crosses a light signal between these two points. In the second category, the emit member and the receive member of the device are generally placed in the same casing. This second category includes systems that are called reflex systems (which may or may not use polarized light), in which a remote reflector can reflect the emitted light signal to the receive member in the absence of a target. Also, the second category includes systems that are called proximity systems (with or without background elimination) that operate using the diffuse reflection of the emitted light signal off the target to be detected.
In the second category, the emit and receive members are therefore very close to each other, in particular in the case of small photoelectric detectors. It is therefore necessary to prevent the phenomenon of crosstalk, i.e., the risk that might arise when the incoming and outgoing light rays become interchanged, which would greatly impair the reliability of the output information from the detector. Moreover, a photoelectric detector often includes lenses placed in front of the emit and receive members in order to improve their sensitivity and their performance and these lenses also increase the risk of crosstalk. Likewise, slight positioning discrepancies between the various members of the detector and a dispersion in the tolerance values from one manufacturing batch to another may increase the crosstalk phenomenon.